Method for protecting metal from erosion

Abstract

1,2-Fused five-membered or six-membered 1,3-dinitrogen-heterocyclic compounds, useful as anti-corrosion agents, having the formula ##STR1## wherein A is an optionally substituted, optionally polynuclear orth- or peri-arylene radical and B is an optionally substituted alkylene chain ##STR2## WHEREIN R 1 and R 2 individually represent hydrogen and/or optionally substituted aliphatic, cycloaliphatic, araliphatic or aromatic radicals and n represents a number from 3 to 6, Or B is an optionally substituted 1,8-naphthylene, 2,2'-diphenylene or 4,5-phenanthrylene radical, Are prepared by splitting a five-membered or six-membered 1,3-dinitrogen-heterocyclic compound, which contains a 2-(ω-amino group) side chain, having the formula ##STR3## wherein A and B have the meanings indicated above and R 3 and R 4 are hydrogen, lower alkyl, cycloalkyl or aralkyl but at least one of the two radicals R 3 and R 4 must represent hydrogen.

What is claimed is: 
     
       1. Method for protecting metal from erosion comprising treating the metal with a compound having the formula ##STR32## wherein A is an arylene radical and B is unsubstituted or halogen, lower alkyl, CF 3 , alkoxy, aryloxy or dialkylamino substituted alkylene chain ##STR33## wherein R 1  and R 2  individually represent hydrogen and/or unsubstituted or halogen, lower alkyl, CF 3 , alkoxy, aryloxy or dialkylamino substituted aliphatic, cycloaliphatic, araliphatic or aromatic radicals and   n represents a number from 3 to 6, or     B is unsubstituted or a halogen, lower alkyl, CF 3 , alkoxy, aryloxy or dialkylamino substituted 1,8-naphthylene, 2,2'-diohenylene or 4,5-phenanthrylene radical.   
     
     
       2. Method of claim 1 wherein A is a naphthylene, phenylene, or diphenylene radical, R 1  and R 2  are, individually, hydrogen, a straight or branched chain aliphatic radical containing up to 8 carbon atoms, an araliphatic radical containing from 7 to 12 carbon atoms, unsubstituted or a halogen, lower alkyl, CF 3 , alkoxy, aryloxy or dialkylamino substituted naphthyl- or phenyl radical and R 3  and R 4  are, individually, hydrogen, a straight or branched chain aliphatic radical containing up to 12 carbon atoms, a cycloaliphatic radical containing up to 8 carbon atoms, or an araliphatic radical containing from 7 to 12 carbon atoms. 
     
     
       3. Method of claim 1 wherein A is a 2,3- or 3,4-pyridylene radical, a 1,2-,2,3- or 1,8-naphthylene radical or a 1,2-phenylene radical each optionally substituted by an alkyl group containing from 1 to 6 carbon atoms, R 1  and R 2  independently represent hydrogen, an alkyl radical containing up to 6 carbon atoms, a cyclopentyl radical, a cyclohexyl radical, a benzyl radical or a phenyl radical, and n is an integer of from 3 to 6. 
     
     
       4. Method of claim 1 wherein A is phenylene, naphthylene, optimally substituted by lower alkyl and halogen B is ##STR34## R 1  and R 2  are each hydrogen or lower alkyl, and n is 3 to 5.   
     
     
       5. Method of claim 1 wherein the compound is one of the formula ##STR35## in which D denotes a 2,3- or 3,4-pyridylene radical, a 1,2-, 2,3- or 1,8-naphthylene radical or 1,2-phenylene radical, these radicals being optionally substituted, preferably by alkyl with up to 6 C atoms, R 5  and R 6  represent hydrogen or alkyl with up to 6 carbon atoms, cyclopentyl, cyclohexyl, benzyl or phenyl, and   m denotes one of the numbers 3, 4, 5 or 6, the m radicals R 5  and R 6  optionally being different.   
     
     
       6. Method of claim 1 wherein the compound is one of the formula ##STR36## wherein E denotes a substituted or unsubstituted radical selected from the group of 1,2-phenylene, 1,2-naphthylene and 2,3-pyridylene, and F denotes a substituted to unaubstituted radical selected from the group of trimethylene, pentamethylene, 2,2-diphenylene and 1,8-naphthylene.   
     
     
       7. Method of claim 1 wherein the compound is one of the formula ##STR37## wherein E denotes a substituted or unsubstituted radical selected from the group of 1,2-phenylene, 1,2-naphthylene and 2,3-pyridylene, and F denotes a substituted or unsubstituted radical selected from the group of trimethylene, pentamethylene, 2,2'-diphenylene and 1,8-naphthylene.   
     
     
       8. Method of claim 1 wherein the compound is one of the group consisting of 1,2-(3'-tert.-butyl-pentamethylene)-benzimidazole;   1,2-(3'-tert.-butyl-pentamethylene)-naphthimidazole;   1,2-naphthylene-(1',8')-benzimidazole;   4,6-dimethyl-1,2-pentamethylene-benzimidazole;   5,7-dimethyl-1,2-pentamethylene-benzimidazole;   1,2-trimethylene-pyrido-[2,3-d]-imidazole;   1,2-(1'-cyclohexylpentamethylene)-benzimidazole; and   benzimidazo-[1,2-f]phenanthridine.